Lin U.S. Pat. No. 5,116,681 discloses fibers made from blends of polypropylene and polystyrene. Example 2E of Lin shows an elongation of 449% when the fiber contains 2% polystyrene, and no conductive carbon black. Example 4 of Lin shows an elongation of 497% when the fiber contains 2% polystyrene and has a conductive core.
It has now been discovered that the elongation at break for filaments made from a blend of polypropylene and polystyrene can be controlled in such a manner that fine denier filaments have elongations at break exceeding 700%.